“We’re not trying to get humans to avoid pigs — we’re trying to get pigs to avoid humans. Humans are the ones carrying the disease at the moment,” he said.

There are no plans to slaughter the pigs which are believed to have caught the virus from workers and the animals are expected to recover without medical treatment.

The Department of Agriculture has not revealed the area where the affected pig unit was found.

“The disease moves through the herd, clears up, and that is it. They don’t get Tamiflu or anything like that — the poor old pigs just have to work their way through the disease.”.

Although the pandemic strain is known as swine flu, it’s something of a misnomer as H1N1 is believed to be a combination of classical swine flu, a version of avian flu and a strain of human flu. It is thought the strains swapped genetic material to produce the fast-spreading human N1N1 strain. But despite the name, pigs are not regarded as a channel for transmitting the virus to humans.

However, yesterday’s finding was not unexpected, Mr Houston said: “We had all expected more findings of human pandemic flu in pig herds. We’ve seen it sporadically around the world, most recently in Canada, Australia and Singapore, but it’s the first time any pigs in Europe have been identified with the disease.

“We’re looking into how the pigs caught it. In previous findings it had generally been transferred from affected humans to pig herds but so far we haven’t been able to determine where it’s come from.”

The case was confirmed after tests were carried out on a batch of piglets by a private veterinary practice at the Agri-Food and Biosciences Institute last Friday.

DARD said it was providing advice to the affected farm and warned farmers who contract the flu to separate themselves from the pigs as best they can.

The department has developed a voluntary code of practice for pig- keepers to help them reduce the risk of spreading the disease among herds. The Food Standards Agency says swine flu does not pose a food safety risk to humans.